To extract maximum power from a given engine, a continuously variable transmission delivers an average integrated output torque that is inversely proportional to the rotational speed of the output shaft. That is the condition for constant output power, and it also means that the input power remains constant at all output speeds except for small friction losses of the transmission. Such a power characteristic is particularly attractive to maximize the operating efficiency and power output from an internal combustion engine or for meeting varying load conditions from a constant angular velocity source such as an electric motor or a turbine engine.
U.S. Pat. No. 3,960,036 was directed toward an inertial type of transmission which has some of the desired characteristics. The apparatus of this invention is an improvement upon the apparatus of that patent.
The apparatus of this invention is a transmission that accommodates continuous changes of angular velocity of both the input and output shafts. The engine is allowed to operate at the angular velocity for maximum efficiency at a given load. The apparatus does not depend on friction, fluids, or gear changes.
A typical automatic transmission operates between 30% and 90% efficiency. In contrast, the apparatus of this invention operates between 92% and 98% efficiency. More importantly, the apparatus' ability to keep an engine operating at peak power and peak efficiency allows the engine displacement to be reduced by more than half with the same automotive performance.
Rand Corporation's Survey, "How to Save Gasoline: Public Policy Alternatives for the Automobile", Number R-1560-NSF, October 1974, showed that a continuously variable transmission, if used in the United States automobiles, would reduce gasoline consumption by 26% or 71 million gallons per day. This study did not include the benefits of reduced engine displacement. Studies show that the apparatus of this invention will reduce United States gasoline consumption by 38% or 104 million gallons per day.
The apparatus is also useful on a bicycle wherein a rider is a power source who operates most efficiently and comfortably at a substantially constant pedal speed. The apparatus of the invention allows the torque delivered to the wheels of the bicycle to increase as the wheel reduces speed.
The apparatus of this invention is also useful in electric automobiles wherein a shunt wound motor could be used, thereby resulting in a substantial reduction in battery load, electric cables, relays and motor size. In addition, battery life and range would be greatly enhanced by using less than the large outrush current required with the usual direct drive series wound motor.
In a turbine driven car the high angular momentum of a turbine usually requires a continuous match between engine angular drive velocity and the drive wheel spaced. The apparatus of this invention allows the turbine to be driven at a high speed and over a small range of angular velocities while the driven shaft torque and angular velocity is not directly related to the input angular velocity.
Presently locomotives require large torque and speed range which dictates the use of expensive and complex diesel/generator/electric motor drives. These can be eliminated by the apparatus of this invention.
Previous continuously variable transmissions have been too expensive and heavy to use in comparatively low cost utility power equipment. It is expected that this invention will be adopted to reduce such costs.
Trucks need both a large torque range and a wide speed range. In the past they have required a gear box with as many as twenty gear changes. The continuously variable transmission of this invention avoids that requirement.
Obviously a large range of power and torque requirements will need to be designed into the individual apparatus. That is, the bicycle and the truck, for example, would not have the same transmission, although their basic kinematic and dynamics would be similar.